If there's a wikilink in a talk page section heading, when that section is opened on mobile the link has display: block; in the overlay header. This makes the header taller than usual, and covers up the first part of the section's content.
Example with the heading Testing [[foobar]] wikilink
- Visit https://en.m.wikipedia.beta.wmflabs.org/wiki/Talk:Test_ascii_toc
- There is a section titled "this is a title with bold text but it should not appear in overlay title" section. Notice that the "bold" word in that title is bolded. Click on this section.
- After clicking the section, verify that the title in Overlay does not contain any bolded characters and that it appears okay (no weird spacing).